Photography

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176 PROCEEDINGS OF THE AMERICAN

CLADOCERA.

Daphnella brachyura, Lievin. Daphnia cederstromii, Schoedler.
Ceriodaphnia, nov. sp. Chydorus sphmricus, O. F. Mttller. Leptodora
hyalina, Lilljeborg.

[The above forms regarded as new will be described in time for
a paper at the next annual meeting of the Society.]

PHOTOGRAPHY.

The session was opened by Mr. Griffith, the Director, announc-
ing that Messrs. J. D. Cox and W. H.Walmsley had consented to take
charge of the subject of photography by lamplight, in its application
to the microscope.

Mr. Cox, for himself and Mr. Walmsley, stated that the plan they
had thought most likely to be profitable was to give some examples
of actual work on microscopic objects with the camera, interspersed
with discussion of practical questions, and of points suggested by
members of the Society as the illustrations proceeded. Mr. Walms-
ley had consented to perform the manipulations, and he (Mr. C.)
would discuss the steps taken in the intervals when Mr. W. might be
off the platform engaged in the " dark room" work.

Mr. Walmsley first exhibited the apparatus to be used, which is
an improvement upon that which has been frequently illustrated by
engravings in the microscopical journals. The camera is construct-
ed with a door in the side for reaching the inner partition used in
copying photographs, but when this is closed the general construc-
tion does not differ from the common double bellows camera with
conical front for receiving the microscopic tube. The frame for the
extension of the camera and clamping it, is hinged so that it may be
easier to pack for transportation. The ground glass screen at the
back of the camera has a small clear disc in the center, made by
cementing a circular "cover-glass" on the ground glass surface with
Canada balsam, which obliterates the roughness, making this spot
transparent. By this arrangement the ground surface is used for
coarser focusing and the transparent spot for the finer adjustment
of the focus by aid of a Darlot focusing glass.

Mr. Walmsley explained that the only change he had recently
made in his arrangement of the microscope and light was to discard
condensers (with the lower powers) and to be less desirous of secur-

SOCIETY OF MICROSCOPISTS. 1 77

ing extremely brilliant lamplight than formerly. Any good coal-oil
lamp with a broad flat single wick was quite sufficient for the pur-
pose. Of course the rejection of the condensers implied a lengthening
of the time of the exposure of the plate, but his experience seemed
to prove that the increase of excellence in definition and brilliancy
of details more than compensated for the added time employed.
The lenses he should use were Beck's lower powers adapted to pho-
tography by the insertion of a concave lens behind the usual com-
bination of the objective. The plates he should use were the

but any of the standard dry plates for quick
work, Eastman, Diamond, Seed, would give good results.

His developer was an alkaline pyro-gallic acid developer not greatly
varying from the standard developers of that class. The difficulty
of complete exclusion of light from the lecture-room made it
necessary to develop his plates in an adjoining dark room, where he
regretted there was not room also for the members of the society.

Whilst Mr. Walmsley was now busy in arranging the apparatus
and centering an object on the camera screen, Mr. Cox resumed the
discussion by calling attention to the fact that the rejection of con-
densers in illuminating the object, and the consequent increase of
time of exposure, was an application to photo-micrography of the
principle so well known in landscape photography, that if it be de-
sired to bring out the finer details in shadow, some method of
increasing the time of exposure must be used. A similar thing had
been noticed in astronomical photography, where stars too faint to
be seen with the telescope were revealed by the sensitive plate if
the exposure were sufficiently prolonged. It would seem that the
impression was not so much due to the vividness of the light as to
oft-repeated impact of even the faintest light waves. He thought it
might be considered a valuable discovery in the microscopical de-
partment of the work, that it is not the intensest light which is
needed, — nay, that in photography, as in investigation with the
microscope, there is a positive danger of " drawing out " the details,
or at least of injuring them, by too much light. Mr. Walmsley had re-
ferred to the use of lower powers, but within reasonable limits the
same thing was true of the higher powers. In using a tenth or fif-
teenth objective, the speaker had not found it practicable to dispense

178 PROCEEDINGS OF THE AMERICAN

with the condenser as Mr. W. did with a " two-thirds" or a "quarter "
inch; but he had often observed that the mild, soft light of the coal-
oil lamp had, with the higher powers, the same desirable effects
which, with the low powers, were obtained by the rejection of the
condenser. In using sunlight, the intensity of the illumination
makes it difficult to avoid diffraction phenomena; objects seem to
scintillate, especially at broken edges (as of a diatom shell), and are
fringed, both to the eye and in the photograph, with brushes of
light or parallel diffraction lines which interfere with true resolution.
He thought the same difficulties likely to attend the use of electric
light, in some degree at least, and suggested that the practical ex-
ample before us taught the lesson of photographing microscopic
objects with the most reduced light which is consistent with a
reasonable time of exposure. Instead of being impatient to ap-
proximate the sunlight with our artificial illumination, we should
recognize the fact that the cheapest and most easily accessible of all
lamps is as satisfactory in its results as it is cheap and common, if
only you give it time.

Mr. Walmsley now exposed a plate, the object being a section
of Echinus spine and the objective a Beck two-third, adapted for
photography as above stated. Mr. W. explained that if using a
strong light with condensers two or three seconds would be a suffi-
cient exposure, but that without these the exposure would be about
five minutes. The lamp was placed so that the edge of the flame
was toward the object, and about four inches from it. He strongly
advised the use of the adapted objectives (of low and medium
powers) as there was no embarrassment when using them with the
question whether the visual and actinic focus were the same. One
had simply to make the sharpest and best picture possible on the
camera screen, and if the table were steady and there was no
" springing " of the parts of the apparatus, the result was reasonably
sure to be a success. In response to a question, he said he used the
microscope without the eye-piece in this work, but as he rarely went
beyond an amplification of four or five hundred diameters, he would
not affirm as to the desirability of doing this with the highest
powers.

When the plate was taken to the dark room for development, the

SOCIETY OF MICROSCOPISTS. 1 79

discussion returned to the use of the eye-piece in photographing.
Mr. Cox said that his own work had been almost exclusively with
amplifications ranging from 750 to 2,000 diameters, and that for this
work he invariably used the microscope with the eye-piece. In
using low powers, and especially in using objectives adapted for
photography, there were reasons why it would sometimes be con-
venient to omit the eye-piece. It might be necessary to do so for
the purpose of getting an illuminated field large enough upon the
screen of the camera, or to reduce the amplification whilst using a
favorite objective. With high powers, however, the consideration
which is decisive with him is that the microscope was made to be
so used. It is a compound instrument. The optician has con-
structed it with reference to use with the eye-piece. He has labori-
ously corrected the imperfections which the eye-piece discloses.
To take away the eye-piece, therefore, is to risk undoing some of
the corrections which the optician has labored upon, and to injure
the image instead of improving it. To argue, therefore, that remov-
ing the eye-piece is to remove also a cause of injury to the image
seemed to him illogical. No one would say it would help an objec-
tive to take out a lens from its system. It might be desirable to
make an objective with fewer lenses; but once made, it must be
used as was intended by the maker. Although the argument as to
the eyepiece does not go "on all fours" with this, it is analogous.

But it should also be remembered that before undertaking to
photograph a delicate object, it has been studied under certain con-
ditions. We have carefully adjusted the objective for the thickness
of the cover-glass; we have used a particular eye-piece and perhaps
a particular obliquity of light. Is it not reasonable to expect the
most satisfactory results when we reproduce, as far an possible, the
conditions under which we obtained the best picture for the eye ?
May not a change of any of these conditions involve a change of
the others ? If the photograph does not show us what we saw in the
instrument, it will be very unsafe to say that this is a more accurate
picture than the one we saw. When we have changed the con-
ditions under which the picture was produced, we have no means of
determining the extent to which this may have introduced error;
certainly we have no scientific ground on which to affirm that we

l8o PROCEEDINGS OF THE AMERICAN

have increased the accuracy of the representation. We should aim
to reproduce what we saw under the most carefully adjusted con-
ditions and after the most sedulous care to correct the instrument
properly in all respects. That is, as it would seem, the only possi-
ble test of the performance of such an optical instrument as the
microscope.

Mr. Walmsley having returned with an ex'cellent negative of the
object photographed, the discussion turned upon the making of paper
prints. After describing the usual silver print process, Mr. W. ex-
hibited some beautiful specimens of the permanent bromide prints.
The advantage of these is found in the fact that the printing may
be done by lamplight and with great rapidity. The developing pro-
cess takes about as much time as the toning of the silver print, and
about as much labor. For many subjects, Mr. W. said, the rough
surface of the bromide paper gives an admirable effect. If a smooth
and burnished surface is desirable it may be obtained by " squil-
geeing" the print, surface down, upon a smooth plate of hard vul-
canite rubber and letting it dry in that situation. If it is desirable
to save the time of toning and fixing the silver prints, or developing
the bromide prints, the best and most rapid process known is the
"blue printing " as the ferro-prussiate process is called.

Mr. Cox stated that he had been surprised to find how much
difference there was in the time taken to make blue prints by means
of different samples of paper. He had formerly supposed, from his
experience with ordinary brands of imported ferro-prussiate paper,
that from three to five times as long an exposure to the sun would
be needed to make a blue print as was necessary for a silver print,
and this went far to counterbalance the saving of time and trouble
by getting rid of the toning and fixing processes. He had found,
however, that the "blue " papers varied greatly in rapidity, and some
samples which he had lately used had required only half the average
time of silver printing. He had not leisure to prepare his own
paper and was obliged therefore to buy it at the shops, and sug-
gested that those who had experience on the subject should give
information.

Mr. Woolman inquired whether part of the difficulty was not in
the stateness of the paper; he had found freshly prepared paper the

SOCIETY OF MICROSCOPISTS. iSl

more rapid in printing, and that to keep it good it must be carefully
protected from both light and moisture. Paper is specially made
for this purpose in the United States, in Germany and in France.
It is in rolls of varying widths and thicknesses. For microscopical
work he would recommend the "extra thin" paper, and that the
members should prepare it themselves so as to be sure it is fresh.

Mr. Cox said he had found no change in paper used by him after
keeping it several weeks; but he was very careful to keep it in a dry
closet and to roll it in "needle paper," or the orange envelope paper,
turning in the wrapping paper at the ends so as to exclude all light.

Mr. Ailing said he could recommend paper made for this pur-
pose by the Hurlbut Paper Company, South Lee, Mass. It was fur-
nished in different thicknesses and sized.

Mr. Cox said it might be well to add a word of warning against
using any blotting paper to dry or to pack the blue prints, except
such as was known to be clean. He had once packed some damp
prints between blotters which had been received from Mr. Walmsley
with some silver paper which had been packed in them. To his
surprise he had found these blue prints afterwards spotted with
white as if flour had been sprinkled over them. He could only
guess that the sheets of blotting paper had been saturated with car-
bonate of soda as was sometimes done to help preserve the sensi-
tiveness of the silver paper, but he was not chemist enough to know
how this had affected the blue prints. A friend who had seen them
had doubted whether the soda could have caused the difficulty, as-
suming that the blue was a "Prussian blue," which is almost unal-
terable.

Mr. Walmsley said it was the fact that his silver prints had been
packed as Mr. Cox guessed, in blotting paper containing carbonate
of soda; but he left others to tell how this affected the blue prints.

Mr. Stratton agreed with those who had recommended that the
paper be prepared by him who used it, in order to secure freshness.
He should not choose to keep it more than a week or two and then
only by putting it in a thoroughly dry and dark place. A good
linen " ledger paper," which can be got at any printer's, he found
excellent for this purpose, though unalbumenized photographic
paper is probably the best.

Io*2 PROCEEDINGS OF THE AMERICAN

The formula he used was :

!Red prussiate of potash I oz.
Water 6 oz.

I Citrate of iron and ammonium I oz.

i< Water 4-oz.

( Citric acid 10 to 20 gr.

Mix equal quantities of a and b, and apply to the paper with a
swab made of Canton flannel wound a stick eight inches long, so
that the whole width of eight inches may be used to apply the mix-
ture evenly to the paper. The paper may be laid flat on a table to
dry, and should be perfectly dry before using.

Mr. Charles Ehrmann spoke in substance as follows :

*' It has been mentioned here how Prof. Pickering, of Harvard
College, has been enabled to photograph the optically invisible neb-
ulse of the Pleiades. As well as Victor Schumann and Captain
Abney have photographed the ultra red of the spectrum upon ortho-
chromatic, that is, color-sensitive plates, may not the learned pro-
fessor have been induced to use that kind of plates for his astro-
photographic experiments ? The idea suggested itself to me, as I
have been informed Prof. Pickering has experimented with hyaline.

"Several inquiries have been made of me in the course of this
day, as to a possible application of colored plates in photomicrog-
raphy. There can hardly be any doubt as to their practicability,
and an advantageous result of their use, in many cases, but it must
be left to the specialist to experiment in that direction.

" By my own experience I am led to advise those feeling inclined
to take up ortho-chromatic photography to adopt the methods of
Messrs. Mallmann & Scolic, of Vienna, which may be found in
detail in the later numbers of The Photographic Times.

" If I had to make blue prints in large numbers, I would discard
paper prepared long before it is used. Its sensitiveness decreases
by age, a decomposition takes place before exposure, aud conse-
quently perfectly pure whites are difficult to obtain. The formula
I have employed to make blue paper is as follows:

\

Ferricyanide of potassium 1 oz.

b.

"' } Water. 4 oz.

( Ammonio-citrate of iron I oz.

( Water 4 oz.

Mix equal volumes of the two solutions and spread over a sheet of
Rives plain paper, by means of a tuft of cotton or a Buckles brush

SOCIETY OF MICROSCOPISTS. 183

and hang up to dry. I select large crystals of the prussiate, wash
them, to liberate them from any decomposed salt adhering, and dry
with bibulous paper, before I weigh out the quantity wanted.

"About ten per cent, more of the iron solution tends to give the
print more vigor and brilliancy. Many beginners in photography
complain of week prints; they simply do not print deep enough.

" The blue deposit is not, as has been stated, Prussian blue, but
Trombull blue, resulting from Ferro-cyanide of potassium and a
ferrous salt."

Mr. Vorce gave the results of considerable experience with blue
prints or cyanotypes, embodying several formuke which he had
tested, with remarks upon the same, as follows:

FORMULAE FOR PREPARING THE SAME.

No. i. A quick-printing paper for immediate use, keeps good

for a few days, but prints slower as it gets older:

]Jr Ferricyanide of potassium (red prussiate of potash) % oz.

Ammonio-citrate of iron 1% oz.

Dissolve each in 8 fluid oz. distilled water, mix as soon as dissolved

and use immediately. Coat the paper evenly with a wide brush, so

as to leave no streaks, and blot off excess of solution to prevent

spottiness. Dry in a current of cool air in the dark. Print in

direct sunlight according to negative, but not too deep. Wash in

clear running water in the dark until the high lights and unprinted

parts are a clear, pure white; then dry. The above formula gives

a bright, clear blue color.

No. 2. English formula; paper keeps longer, but prints slower

than the above; gives a slightly darker blue.

ffe < Ferricyanide of potassium.., I oz.

( Water 8 oz.

I Ammonio-citrate of iron I oz.

( Water 8 oz.

Treatment same as above.

No. 3. Commercial formula. Used by engineers, draughtsmen

and many others for copying plans, drawings of machinery, etc.

Rather a slow printing paper, but strong, dark color.

Ijc j Ferricyanide of potassium I oz.

Water 4 oz.

Ammonio-citrate of iron 1 oz.

Water 4 oz.

Treatment same as before described.

184 PROCEEDINGS OF THE AMERICAN

No. 4. A good printing paper when fresh, slower than No. 1,
but darker color, and giving good contrasts.
fj; By weight.

Ferricyanide of potassium 16 parts.

Water 100 "

Ammonio- citrate of iron 24 "

Water 100 "

Gum acacia 2 '*

Water 100 "

Mix equal volumes of the two solutions. Treatment same as in
other cases.

GENERAL REMARKS.

i. The paper used for blue prints should be free from any trace
of soda to insure permanency of the prints. No better paper can be
found for the purpose than that known as "photographic plain
paper," since all papers prepared for photographers' use are free
from soda. Albumen paper can be used for cyanotypes, but is more
difficult to coat evenly in large sheets than plainer paper.

2. The water used for all the solutions should be distilled, or at
least free from lime or soda. And the purer the water used for
washing the prints the better will be the result.

3. The solutions should always be mixed immediately before
use, and should be used in the dark. A good plan is to mix the so-
lutions and coat the paper in the evening, which may be done by
gaslight, and hang it in a dark closet or room to dry. In the morn-
ing the paper will be dry and can be put into light-tight boxes until
used, which should be done the same day, if possible, as it works
much better when fresh. One ounce of the mixed solution will coat
ten or twelve square feet of paper if carefully used.

4. The paper should be printed to a steel gray color in the
lights, and the washing is best done in running water and in the dark
or by gaslight. Washing by daylight will not spoil the print if the
washing is not too prolonged.

5. Over-printed prints can be reduced by a very weak solution
of carbonate of soda, but are not likely to be permanent; and the
prints are so cheaply and quickly made that it is wasting time to try
to improve a bad print by reducing or otherwise.

The beautiful-plates of diatoms in Schmidt's Atlas, which were
copied and reduced by Prof. C. H. Kain, of Camden, N. J., in
cyanotype, show how finely detail is reproduced by this process.

SOCIETY OF MICROSCOPISTS. 185

The plates printed by Prof. Kain were by formula No. i, above
given, which is stronger in iron than any of the others. The bright
color of his plates for that class of work seems preferable to a
darker color. The prints of butter and fat crystals exhibited by
Dr. H. J. Detmers, of Columbus, O., at the present meeting, were
produced by formula No. 4, furnished by Prof. A. H. Tuttle. The
prints of diatoms exhibited by Hon. J. D. Cox, at the Cleveland
meeting were, in all probability, produced by formula No. 3, as that
formula is given in many books and is much used.

There is a method of cyanotype printing in which the paper is
sensitized in a solution of an iron salt, and after printing developed
in a solution of the potassium salt; but it is much more troublesome
and no better than the usual method as above described.
THE GENERAL SESSION.

The exhibitors were promptly at their tables pursuant to adjourn-
ment. A printed programme had been distributed,' giving briefly
the work to be accomplished at each of forty tables arranged by
those in charge about the spacious room, and most convenient for
the large number of the Society and others who witnessed the work
that interested them most.

Some for whom a plan had been prepared were not able to at-
tend; in the following account of the individual work the members
of unoccupied tables are omitted.

No. 1. Dr. C. M. Briggs, of Fairport, N. Y., placed a drop of
fresh blood a little to the left of the center of the slide, and another
slide, with the edge placed crosswise and at an angle, was drawn
from left to right, thus wiping off most of the blood and leaving a
thin layer of blood discs flatwise on the slide. This is allowed to
dry, then the slide is placed on the turn-table, centered, and the blood
turned down to a circle of the desired size. To stain the corpuscles,
the slide is flooded with a solution of eosine and allowed to stand
from three to five minutes, then flooded with water to wash it, and
again allowed to dry, after which a small drop of balsam and benzole
is placed on the slide, covered and heated cautiously. A little prac-
tice will enable anyone to mount blood nicely in this way.

No. 4. Mr. W. H. Brearly, Detroit, Mich., exhibited a portable
holder for optical instruments.